在Django表单中验证ModelChoiceField

Question

我正在尝试验证一个包含 ModelChoiceField 的表单：

forms.py：

from django import forms

from modelchoicetest.models import SomeObject

class SomeObjectAddForm(forms.ModelForm):
    class Meta:
        model = SomeObject

models.py：

from django.db import models

class SomeChoice(models.Model):
    name = models.CharField(max_length=16)

    def __unicode__(self):
        return self.name

class SomeObject(models.Model):
    choice = models.ForeignKey(SomeChoice)

views.py：

from django.shortcuts import render_to_response
from django.template import RequestContext
from django.http import HttpResponseRedirect
from django.core.urlresolvers import reverse

from forms import SomeObjectAddForm

def add(request):
    if request.method == 'POST':
        form = SomeObjectAddForm(request.POST)
        if form.is_valid():
            form.save()
            return HttpResponseRedirect(reverse('modelchoicetest_add'))
    else:
        form = SomeObjectAddForm()

    return render_to_response('modelchoicetest/index.html',
                              {'form': form},
                              context_instance=RequestContext(request))

在正常情况下使用时，一切都很顺利。但我想要保护这个表单，避免无效输入。很明显，当我在这个字段中输入无效值时，我应该得到 forms.ValidationError，对吧？但是如果我尝试提交一个在 'somechoice' 字段中填入 'invalid' 的表单，我得到的是：

ValueError: invalid literal for int() with base 10: 'invalid'

而不是预期中的 forms.ValidationError。我该怎么办呢？我尝试在这里放一个 def clean_somechoice(self) 来检查这个字段，但那并没有奏效：ValueError 在它到达 clean_somechoice() 之前就发生了。

而且我觉得这不是一个好的解决方案，应该有更简单的方法，但我就是没想到。

这是完整的错误追踪信息：

Traceback:
File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/base.py" in get_response
  101.                     response = callback(request, *callback_args, **callback_kwargs)
File "/home/andrey/public_html/example/modelchoicetest/views.py" in add
  11.         if form.is_valid():
File "/usr/local/lib/python2.6/dist-packages/django/forms/forms.py" in is_valid
  120.         return self.is_bound and not bool(self.errors)
File "/usr/local/lib/python2.6/dist-packages/django/forms/forms.py" in _get_errors
  111.             self.full_clean()
File "/usr/local/lib/python2.6/dist-packages/django/forms/forms.py" in full_clean
  276.                     value = field.clean(value)
File "/usr/local/lib/python2.6/dist-packages/django/forms/fields.py" in clean
  154.         value = self.to_python(value)
File "/usr/local/lib/python2.6/dist-packages/django/forms/models.py" in to_python
  911.             value = self.queryset.get(**{key: value})
File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py" in get
  330.         clone = self.filter(*args, **kwargs)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py" in filter
  536.         return self._filter_or_exclude(False, *args, **kwargs)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/query.py" in _filter_or_exclude
  554.             clone.query.add_q(Q(*args, **kwargs))
File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py" in add_q
  1109.                             can_reuse=used_aliases)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/query.py" in add_filter
  1048.                 connector)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/where.py" in add
  66.             value = obj.prepare(lookup_type, value)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/sql/where.py" in prepare
  267.             return self.field.get_prep_lookup(lookup_type, value)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/fields/__init__.py" in get_prep_lookup
  314.             return self.get_prep_value(value)
File "/usr/local/lib/python2.6/dist-packages/django/db/models/fields/__init__.py" in get_prep_value
  496.         return int(value)

Exception Type: ValueError at /
Exception Value: invalid literal for int() with base 10: 'invalid'

django 错误处理表单验证数据验证 web开发表单字段 modelchoicefield forms.validationerror

在Django表单中验证ModelChoiceField

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